The Jawaharlal Nehru University administration said students agitating over the hike in hostel fees "ransacked" the server room and "intimidated" the technical staff on Saturday, hampering the semester registration process.
But JNUSU said the administration used "masked" security guards to attack students. "They were shamefully wearing masks. JNUSU president was openly slapped by one of the security guards," alleged the students' union, which has called for a boycott of the process over the increase in hostel fees.
The semester registration process will end on January 5.
The university has been seeing a standoff between the students and the administration over hike in hostel fees for over 70 days. Students even boycotted exams in protest, prompting the administration to send question papers to students through WhatsApp and email, a move condemned by the union.
Explaining the events, the university said the technical staff gained access to the communication and information services (CIS) premises Saturday morning, after the servers were made dysfunctional by students on Friday, with the help of security guards and rebooted the servers, the university said.
But a group of "miscreants" entered the server room, intimidated the staff, and damaged the systems around 1pm, it alleged.
Around 4pm, the staff once again gained access to the CIS room and were trying to restore the systems.
Appealing to students to continue the boycott of the registration process, the JNUSU claimed the administration is "extremely rattled" by the unity of students.
Meanwhile, the RSS-affiliated Akhil Bharatiya Vidyarthi Parishad said its members protested against the disruption of internet, after which they were attacked by the members of the Left Unity.
The JNUSU alleged that students were attacked by ABVP members.